1. Field of the Invention
The present invention relates generally to weight measuring devices. More particularly, the invention concerns a method and apparatus for determining the axle weight of a railroad car by sensing the deflection in portions of the rails of the railroad track over which the railroad car is passing.
2. Discussion of the Invention
It has been a common practice in the past to use load cells for measuring the weight of various types of articles or materials, such as those contained within tanks and hoppers. Such measurements have typically been accomplished through the use of load cells that are positioned beneath the article to be weighed. However, in order to install the load cells, the article must generally be raised and, in the case of tanks and hoppers, in many instances, the legs of the tank or hopper must be cut or otherwise structurally modified in order to install the load cells. For these reason, the use of conventional load cells for such weighing operations is undesirable and can result in rather substantial expenditures, inconvenience, and time delays in the installation of the load cells.
Another prior art approach sometimes used for measuring the weight of articles or materials contained within supporting structures involves the use of strain gauge devices that are mounted within drilled holes formed in the structural members of the supporting structure. In such instance, the strain gauges are adapted to measure the deformation of the hole in the structural member as the load is increased. Typically the installation of such strain gauge devices is difficult and the reliability of such measurements is frequently suspect.
To overcome the drawbacks of prior art measuring systems of the character described in the preceding paragraphs, the present inventor developed a novel clamp-on structural strain gauge sensor that can be mounted to dynamic load bearing structures such as sucker-rod type oil well pumps to produce an electrical output proportional to the deflection of the structures. This novel strain gauge measuring apparatus is disclosed in U.S. Pat. No. 5,423,224 issued to the present inventor. Because of the pertinence of this patent to an understanding of the present invention, U.S. Pat. No. 5,423,224 is hereby incorporated by reference as though fully set forth herein.
In one embodiment of the invention described in U.S. Pat. No. 5,423,224, the strain measuring apparatus of the invention can be used in conjunction with conventional weighing instrumentation such as a Weigh Meter and has the ability to convert the analog signal from the strain gauge apparatus to a digital signal for processing and correction and then to reconfigure the data back to analog signals for input to the Weigh Meter.
As will be better understood from the discussion of which follows, the method and apparatus of the present invention makes use of a somewhat similar strain gauge sensors to those described in U.S. Pat. No. 5,423,224 to precisely determined the weight of each axle of each of the rail cars of a railroad train passing over the section of railroad track to which the strain gauge sensors have been interconnected.
It is an object of the present invention to provide a method and apparatus for determining the weight of each axle of a plurality of rail cars of a railroad train passing over a selected section of a railroad track.
Another object of the invention is to provide an apparatus of the aforementioned character which embodies a portable measuring device that, when clamped to the selected section of the railroad track, measures strain induced in a portion of the track as the rail car passes over that portion of the track to produce an electrical output which is precisely proportional to the load imposed on the portion of the track as each axle of the rail car passes over the portion of the track.
Another object of the invention is to provide an apparatus of the character described that readily interfaces with a remotely located data processing subassembly that receives the output from the strain gauges and precisely determines the axle weight therefrom.
Another object of the invention is to provide an apparatus as described in the preceding paragraphs, which is completely portable and can be quickly and easily interconnected with each rail of the railroad track by relatively unskilled workers using conventional tools.
Another object of the invention is to provide an apparatus of the class described which includes sensor means for first sensing the proximity of the wheels of the rail car to the sensors that are connected to the track and for then activating the strain gauge sensors to measure deflection in the rails caused by the rail car passing thereover.
Yet another object of the invention is to provide a method and apparatus of the character described which enables the precise measurement of each axle of each rail car of the railroad train as the train moves along the track without requiring that the train be stopped at the sensor locations.
Still another object of the invention is to provide a method and apparatus of the character described which includes novel calibration means for on site calibration of the apparatus.
In summary, the foregoing objects of the invention are achieved through the use of a strain gauge sensors that are removably connected to sections of the rails of the railroad track over which the rail cars pass through the use of proximity sensor means for sensing the proximity of the wheels of a rail car to the strain gauge sensors to produce an electrical output proportional to the deflection of the sections of the rails caused by the passage of the rail car thereover; and through the use of a data processing subassembly, which the electrical output is transmitted to convert the electrical output into the weight of the axle of the rail car passing over selected the sections of the railroad track.